Fire Weather Index

Chandler Burning Index Description

LOW
<50

MODERATE
50-75

HIGH
75-90

VERY HIGH
90-97.5

EXTREME
<97.5

The Chandler Burning Index (CBI) uses the air temperature and relative humidity to calculate a numerical index of fire danger. That number is then equated to the Fire Danger severity of either extreme, very high, high, moderate, or low. It's based solely on weather conditions, with no adjustment for fuel moisture. Here at Chatteris Weather, the CBI is calculated from the current weather conditions and reflects the current calculated fire danger.

Fire Danger Rating

Description

Low (L) (Blue)

Fuels do not ignite readily from small firebrands although a more intense heat
source, such as lightning, may start fires in duff or punky wood. Fires in open cured grasslands may burn freely a few hours after rain, but
woods fires spread slowly by creeping or smoldering, and burn in irregular fingers. There is little danger of spotting.

Moderate (M) (Dark Blue)

Fires can start from most accidental causes but, with the exception of lightning
fires in some areas, the number of starts is generally low. Fires in open cured grasslands will burn briskly and spread rapidly on windy
days. Timber fires spread slowly to moderately fast. The average fire is of moderate intensity, although heavy concentrations of fuel,
especially draped fuel, may burn hot. Short-distance spotting may occur, but is not persistent. Fires are not likely to become serious and
control is relatively easy.

High (H) (Yellow)

All fine dead fuels ignite readily and fires start easily from most causes.
Unattended brush and campfires are likely to escape. Fires spread rapidly and short-distance spotting is common. High-intensity burning may
develop on slopes or in concentrations of fine fuels. Fires may become serious and their control difficult unless they are attacked
successfully while small.

Very High (VH) (Orange)

Fires start easily from all causes and, immediately after ignition, spread rapidly and increase quickly in intensity. Spot fires
are a constant danger. Fires burning in light fuels may quickly develop high intensity characteristics such as long-distance spotting and
fire whirlwinds when they burn into heavier fuels.

Extreme (E) (Red)

Fires start quickly, spread furiously, and burn intensely. All fires are potentially serious. Development into high intensity
burning will usually be faster and occur from smaller fires than in the very high fire danger class. Direct attack is rarely possible and
may be dangerous except immediately after ignition. Fires that develop headway in heavy slash or in conifer stands may be unmanageable while
the extreme burning condition lasts. Under these conditions the only effective and safe control action is on the flanks until the weather
changes or the fuel supply lessens.